H3

H3, H03 or H-3 may refer to:

Entertainment

Happy Hustle High, a manga series by Rie Takada, originally titled "H3 School!"
H3 (film), a 2001 film about the 1981 Irish hunger strike
h3h3Productions, styled "[h3]", a satirical YouTube channel

Triatomic hydrogen (H₃), an unstable molecule
Trihydrogen cation (H₃⁺), one of the most abundant ions in the universe
Tritium (Hydrogen-3, or H-3), an isotope of hydrogen
ATC code H03 Thyroid therapy, a subgroup of the Anatomical Therapeutic Chemical Classification System
British NVC community H3, a heath community of the British National Vegetation Classification system
Histamine H₃ receptor, a human gene
Histone H3, a component of DNA higher structure in eukaryotic cells
*h₃, one of the three laryngeals in the reconstructed Proto-Indo-European language
Hekla 3 eruption, a huge volcanic eruption around 1000 BC

H3 (rocket), an expendable launch system under development by Japan Aerospace Exploration Agency
Harbour Air Seaplanes (IATA code), a Canadian charter airline
H-3 Air Base, former Iraqi Air Force base in western Iraq
H-3 Sea King, a United States Navy helicopter
Standard H-3, an improved version of the 1916 Standard H-2 aircraft

H3 (classification), a para-cycling classification
H3, an 18th-century marine chronometer by John Harrison
H3, a type of automotive halogen lamp
H3 (pyrotechnics), a pyrotechnic composition
H3 Hardy Collaboration Architecture, a firm started by Hugh Hardy
H3 Pharmaceutical Chemistry, an advanced subject for GCE A-level students in Singapore
DSC-H3, a 2008 Sony Cyber-shot camera
Hash House Harriers, an international group of non-competitive running, social and drinking clubs
H3 (Kuwait), an archaeological site
H3 Entertainment, a subsidiary of the film industry company The H Collective